Forensic psychologist Scott Fraser studies how we remember crimes. He describes a deadly shooting and explains how eyewitnesses can create memories that they haven't seen. Why? Because the brain is always trying to fill in the blanks.

About Scott Fraser

When it comes to witnesses in criminal trials, the accuracy of human memory can mean the difference between life and death. Scott Fraser is a forensic psychologist who researches what's real and what's selective when it comes to human memory and crime. He focuses on the fallibility of human memory and encourages a more scientific approach to trial evidence. He has testified in criminal and civil cases throughout the U.S. in state and federal courts.

In 2011 Fraser was involved in the retrial of a 1992 murder case in which Francisco Carrillo was found guilty and sentenced to two life sentences in prison. Fraser and the team that hired him staged a re-enactment of the night in question, and they showed the testimonies that had put Carrillo in jail were unreliable. After 20 years in jail for a crime he didn't commit, Carrillo was freed.

RAZ: Good thing he did because Scott is actually all about the mind, specifically memory, which is what we're talking about on the show today, memory games. How much can you trust memories and how do you keep them? And in Scott Fraser's case, well, he's focused on what our mind retains, what it doesn't, and why. He's a forensic psychologist.

FRASER: Which involves reviewing case materials, testifying in court cases. In some cases we actually reconstruct the crime scene itself.

RAZ: So I'm thinking you're like a private eye, like, sitting in an office with his legs up on the table and some dame walks in. You're smoking a cigarette. Is that real?

FRASER: (Laughing) It's been so long since a dame walked into any of my offices. It's more like ring ring, ring ring, ring ring...

You answer and, please help me. That's an attorney talking, please help me.

RAZ: Sometimes a prosecutor, sometimes a defense attorney, whoever it is, they call Scott because they're having an issue with the memory of someone who's witnessed a crime. Here's Scott's TED Talk.

(SOUNDBITE OF TED TALK)

FRASER: The murder happened a little over 21 years ago, January the 18th, 1991, in a small bedroom community of Lynwood, California, just a few miles southeast of Los Angeles. Father came out of his house to tell his teenage son and his five friends that it was time for them to stop horsing around, to get home, finish their schoolwork, prepare themselves for bed. And as the father was administering these instructions, a car drove by slowly and just after it passed the father and the teenagers, a hand went out from the front passenger window and bam, bam - killing the father and the car sped off.

Investigating officers were amazingly efficient. They considered all the usual culprits and in less than 24 hours they had selected their suspect, Francisco Carrillo, a 17-year-old kid who lived about two or three blocks away from where the shooting occurred. They found photos of him, they prepared a photo array and the day after the shooting, they showed it to one of the teenagers and he said, that's the picture. So at the actual trial, all six of the teenagers testified and indicated the identifications they had made in the photo array. He was convicted. He was sentenced to life imprisonment, adamantly insisting on his innocence, which he has consistently for 21 years. Oh yes, no gun was ever found, no vehicle was ever identified as being the one in which the shooter had extended his arm and no person was ever charged with being the driver of the shooter's vehicle. The problems, actually, for this kind of case, come manyfold from decades of scientific research involving human memory.

RAZ: And what are those problems? Well, for one thing Scott Fraser says, remember that six teenagers, six of them, picked the suspect, Francisco Carrillo, out of a police lineup.

FRASER: There's lots of research that shows that when we are faced with a lineup, a recognition test of some sort - witnesses and victims are not stalks of asparagus, they're smart. And they're saying, if law enforcement is going to show me photos or take me to a live lineup and that, they probably have a suspect. And that changes the task. You have to keep in mind, all recognition decisions are social judgments. That means it's very, very subjective. It's going to be influenced by all sorts of other factors that have nothing to do with what's left in your memory. All our memories, put simply, are reconstructed memories and they're constantly changing, even as we're talking about them.

RAZ: You know, sometimes, like I'm sure this happens to you too, where your mind plays tricks on you, right. You may have seen a photograph of yourself as a child and then that becomes a memory of something that happened that you remember, but there's almost no way you could've remembered it because you were, you know...

FRASER: Exactly.

RAZ: ...three or four, but you believe that you remember it.

FRASER: Absolutely, we all remember all sorts of things that are really the product of post-experience information. People remember falling out of the crib and it's very unlikely that they have an accurate memory of all those details. But if they've heard the story told about the parents and how upset they were that they had allowed this to occur, there was pictures of you in your pink pajamas and those are the pajamas you were wearing when you fell out of the crib, then it becomes a memory that you actually believe that you experienced. There's research studies that shows that you can get individuals, by giving false information to them from other family members, to believe that something happened to them early in their life that they had no recollection before but now they do remember, for example, being kidnapped by somebody at a mall when it never really happened. So we all look through family albums. We all hear stories at the dinner table and they become assimilated. They become incorporated into what we believe we actually remember.

RAZ: But could there be something else going on, something physiological with our memory, especially in a stressful situation like witnessing a crime?

FRASER: We've all experienced this. If you go and pay good money to go to a horror movie.

RAZ: Okay, so, for example, let's keep it classic with Jaws. You've got a diver searching a boat wreck for a missing fisherman and then he plucks a shark tooth from the wood and you feel something coming.

FRASER: You're sitting in a theater with 400 other people. What's going to happen to you? Where's the danger?

RAZ: The diver's shining his flashlight down the boat's hull, and then a body.

RAZ: ...and right out to your muscles in case you need to run or jump or whatever.

FRASER: The body gets ready immediately.

RAZ: And since you only have so much blood in your body, when you take it from one place...

FRASER: ...you have to reduce blood flow someplace else.

RAZ: The cortex.

FRASER: The top part of the human brain, which is critical for processing information and for storing it so that it will be recalled reliably later. And you're not attending to things such as eyebrows, cheeks, jaws, ears. You are focused solely on survival. How am I going to get out of here alive?

RAZ: Which means later, when you do try to piece together a memory of that stressful moment, well, your brain fills in the gaps.

(SOUNDBITE OF TED TALK)

FRASER: The brain fills in information that was not there. It's called reconstructed memories. It happens to us in all the aspects of our life, all the time. What we know, that we have what, 280 documented cases now where people have been wrongfully convicted and subsequently exonerated, some from death row, on the basis of later DNA analysis. And you know that over three-quarters of all of those cases of exoneration involved only eyewitness identification testimony during the trial that convicted them. That was part of the instigation for a group of appeal attorneys to petition a Superior Court for a retrial for Francisco Carrillo.

They retained me, as a forensic neurophysiologist, because I had expertise in eyewitness memory identification, which obviously makes sense for this case, right. But also because I have expertise and testify about the nature of human night vision. Well, what's that got to do with this? Well, when you read through the case materials in this Carrillo case, one of the things that suddenly strikes you is that the investigating officers said the lighting was good at the crime scene. All the teenagers testified during the trial that they could see very well. But this occurred in mid-January, in the northern hemisphere, at seven p.m. at night. So when I did the calculations for the lunar data and the solar data at that location on Earth at the time of the incident of the shooting, all right? It was well past the end of civil twilight and there was no moon up that night. The only lighting in that area had to come from artificial sources.

RAZ: So Scott visited the crime scene at the same time of night and at the same time of year. And that artificial light, a streetlight...

FRASER: ...coming from behind the perpetrator.

RAZ: And from that angle...

FRASER: ...their face would be in the shadow that's cast by their own head.

RAZ: And with those lighting conditions, it meant...

FRASER: ...that the distance at which you could detect the features that are necessary to reliably recognize the person were probably 12 to 18 inches away from you.

RAZ: But on the night of the murder...

FRASER: ...the car was going by at least three or four feet away from the witnesses.

RAZ: Not only would you have had trouble detecting features from that distance, so would the photoreceptors in your eyes, the ones that see color.

FRASER: Those are called cones. Cones require a certain minimum amount of stimulation, a certain minimum amount of light, to operate. The lighting was so low at the location of the witnesses that the cones would not have been operating to be able to detect color.

RAZ: Which would have made seeing and remembering the shooter's race, it would've made it almost impossible, even though the witnesses were confident they had the right guy.

FRASER: What it indicates is that confidence is not a reliable barometer but yet it's one that we use all the time.

RAZ: We convict people based on...

FRASER: Not only convict, we know that most jury-eligible adults have a very strong belief that eyewitness confidence and certainty is a good indication as to whether or not the person is correct or incorrect.

(SOUNDBITE OF TED TALK)

FRASER: I testified to that to the court and while the judge was very attentive, it had been a very, very long hearing for this petition for a retrial. And as a result, I'd noticed out of the corner of my eye that I thought that maybe the judge was going to need a little more of a nudge than just more numbers. And here I became a bit audacious. I said, Your Honor, I think you should go out and look at the scene yourself.

RAZ: What happened next? That's coming up. I'm Guy Raz and this is the TED Radio Hour from NPR.

(SOUNDBITE OF MUSIC)

RAZ: It's the TED Radio Hour from NPR. I'm Guy Raz and on the show today, memory games, why we remember some things and forget almost everything else. Now, on the last part of the show we heard from Scott Fraser. He's a forensic psychologist who was hired to figure out whether a man named Francisco Carrillo, who was convicted of murder and sentenced to life in prison, whether he was guilty, or whether he was the victim of bad human memories. We pick up where we left off. Scott has just convinced a judge who has to decide whether to grant Carrillo a retrial. Scott convinced him to visit the scene of the crime.

FRASER: We, first of all, picked the date and time when we'd had the same lunar conditions and the same solar conditions, namely after twilight, there was no moon up. We had already established the foundation, all the lights on the street were the same as they were 21 years ago. And on that date, the judge was driven to the scene.

(SOUNDBITE OF TED TALK)

FRASER: He came out with an entire brigade of sheriff's officers to protect him in this community, all right. We had him stand actually slightly in the street, so closer to the suspect vehicle, the shooter vehicle, than the actual teenagers were. So he stood a few feet from the curb toward the middle of the street. We had a car that came by, same identical car as described by the teenagers, it had a driver and a passenger. And after the car had passed the judge by, the passenger extended his hand, pointed it back to the judge as the car continued on, just as the teenagers had described it. Now we didn't use a real gun in his hand, so we had a black object in his hand that was similar to the gun that was described.

And we had the judge look at it. So he looked at the car, went around the block, the arm came out at 30 feet. Car went around the block, the arm came out at 15 feet. So the judge got to look at this car going when the arm came out each time. After he did that, then he asked me if there was anything else that I wanted him to look at and I said, yes, there would be one more thing. I want you to stand right here and I'm going to have the car drive around the block. I want it to stop right next to you, three to four feet away. The window is down. I'm going to have the passenger extend his arm with that black object, and I want you to look at him. Look at the face of the person extending the arm in the car for as long as you want. The defense attorneys for Mr. Carrillo thought I was being probably absolutely stupid, but I had the confidence in my measures that the depth of detail detection was going to be 18 inches or less. So we had the car drive around, stop right in front of the judge, arm came out, and the judge stared at it. Stared at it. And what you see is, in fact, almost a totally black, flat screen. You can't even see the arm sticking right out at you.

(SOUNDBITE OF TED TALK)

FRASER: There was a few more days of evidence that was heard. At the end of it, he made the judgment that he was going to grant the petition for a retrial. And furthermore, he released Mr. Carrillo so that he could aid in the preparation of his own defense if the prosecution decided to retry him, which they decided not to. He is now a freed man.

(APPLAUSE)

FRASER: And what does this example, what's important to keep in mind for ourselves? I constantly have to remind myself about just how accurate are the memories that we know are true. None of those teenagers thought that they were picking the wrong person. None of them thought they couldn't see the person's face. We all need to remember to be cautious, that the accuracy of our memories is not measured in how vivid they are nor how certain you are that they're correct. All our memories are reconstructed memories. Thank you.

(APPLAUSE)

RAZ: Scott Fraser. That case, by the way, isn't over. Francisco Carrillo is now suing the county of Los Angeles. The teenage witnesses who identified him have since recanted. Two other men have confessed to the shooting. Transcript provided by NPR, Copyright NPR.